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There are two frame VI gas turbines installed with Mark V control system and had been running in 4 % droop mode in island condition with load of 21 & 22 MW on each machine.
There was a sudden load due to disturbance in connected load and frequency dropped to 48.75 Hz from 50 Hz within 5 Seconds. In the same 5 seconds, load increased on each GT's by 5 & 6 MW respectively. But till that time there was load throw off in the connected process load on under frequency setting of 48.75 Hz. After sudden load throw off, machine got over speed and tripped.
We are not able to find out if there is any defined load ramp rate in the Mark V, as why machine did not go to base load which if it could have, process plants would not have tripped.
There was a sudden load due to disturbance in connected load and frequency dropped to 48.75 Hz from 50 Hz within 5 Seconds. In the same 5 seconds, load increased on each GT's by 5 & 6 MW respectively. But till that time there was load throw off in the connected process load on under frequency setting of 48.75 Hz. After sudden load throw off, machine got over speed and tripped.
We are not able to find out if there is any defined load ramp rate in the Mark V, as why machine did not go to base load which if it could have, process plants would not have tripped.